Write drivers for write heads of a magnetic disk drive are employed to provide a write current to the write heads. A flex/interconnect is generally used to connect the write driver to the write head. A write driver generally requires a wide bandwidth and a fast rise/fall time of the write current, an adjustable overshoot of the write current to compensate high frequency losses, an output impedance matched to the input impedance of the flex/interconnection, a low power consumption, and a fast recovery from read to write mode, etc.
Conventional techniques have been utilized to address these requirements, for example, using a switchable “H-Bridge”, switchable differential transistors, and the like. However, these conventional approaches add the boost or overshoot of the write current at the output stage of the circuit. The disadvantage of this is that the write driver circuit needs extra transistors to be connected to the write head to adjust the overshoot. Those extra transistors increase the output capacitance of the write driver, and that in turn, make it difficult to achieve high bandwidth and to match the output impedance of the write driver to the input impedance of the interconnections.
Accordingly, there is a need for a write driver that not only has a wide bandwidth and a low power consumption, but also matches both differential and common mode output impedance to the impedance of the flex/interconnect.